1. Field of the Invention
The present invention is related to combustible fuels, such as those used in boiler operations for the purpose of producing steam as an energy source. More particularly, the present invention is directed to a mixture of partially hydrogenated vegetable oil and diesel fuel to be used as a combustible medium. The present invention is also directed to a method of operating a diesel boiler with such a mixture and a process for producing such a mixture.
2. Description of the Related Art
Companies today are searching for alternative renewable, cleaner burning energy sources, particularly for industrial use, for environmental and regulatory reasons. Further, limited resources of natural gas, diesel fuel and coal has created a further need for such alternative fuel sources.
In particular, a typical combustion medium in boilers is pure diesel fuel. When pure diesel fuel is burned in a boiler, the smoke stack associated with the boiler will output an emission with a significant sulfur content. Since a high sulfur content in the outputted emission is considered hazardous for the environment, these emissions are the subject of considerable government regulations. As a result of such environmental concerns and regulations, there is a need for fuels with reduced sulfur content. This need is expected to be even greater in the future as new and stricter regulations on exhaust emissions will require even lower sulfur levels.
Additionally, it is desirable to lower the cost of fuel for a boiler and to reduce reliance on pure diesel fuel. As a result, there is a need for a fuel which is something other than pure diesel fuel and which can be less costly than a fossil fuel. The use of partially hydrogenated vegetable oil and diesel fuel may in some circumstances be less costly than diesel fuel alone.
There have been a variety of attempts to produce an acceptable alternative fuel composition. For example, in U.S. Pat. No. 5,578,090 (Bradin), biodiesels of esters of free fatty acids and ethers of glycerol with oil were tried. These esters, for example, are formed in the presence of acid as a catalyst. However, the method for producing such a biodiesel involves refining or processing of the fuel additive composition before it can be used as a combustible medium in a fuel boiler. In particular, these biodiesels require additional processing to chemically cleave free fatty acids from vegetable oil molecules. In this prior approach, the esters of free fatty acids are created by a reaction with either methanol or glycerol. These free fatty acids, however, are extremely corrosive and difficult to handle once isolated. Further, the additional steps necessary for this process are costly and inefficient.
Prior products have included certain other additives added to hydrocarbon oils. For example, U.S. Pat. No. 2,243,198 (Dietrich) is directed to the addition of a hydrogenated castor oil derivative to a non-viscous normally liquid hydrocarbon oil. The castor oil derivative, however, is added to increase lubricity and decrease the pour point of the liquid hydrocarbon oil. Further, the castor oil is used in such a small amount (0.1–2%) that the hydrocarbon oil in Dietrich '198 cannot really be considered an alternative fuel source in as much as the castor oil is unlikely to significantly impact the cost of the hydrocarbon oil or the emission output if they were to be used as a boiler fuel, for example. Dietrich '198 also uses a hydrogenated castor oil derivative which requires additional processing and expense to produce.
Another fuel oil composition is disclosed in U.S. Pat. No. 6,265,629 (Fava et al.) In this patent, a heavy gas component, such as a transesterfied vegetable oil, is used to enhance the lubricity of fuel oil. The transesterfication of the oil represents an addition expense which is a consequence of this process.
U.S. Pat. No. 4,992,605 (Craig et al.) discloses a process for producing liquid paraffinic hydrocarbons in the C15–C18 range. The hydroprocessing in the process disclosed in Craig et al. '605 is a severe process, which not only hydrogenates the oil, but also breaks the chemical structure to form paraffinic hydrocarbon chains. The resulting structure is not a vegetable oil. Further, it is an additive, rather than a fuel source to be used as an energy source.
It is accordingly a general object of the present invention to overcome each of the noted drawbacks in the prior art. An object is to provide improved products and methods which produce a fuel mixture of partially hydrogenated vegetable oil and #2 diesel fuel. This fuel mixture may be more cost effective, is a renewable energy resource and emits a lower sulfur content when burned, when compared with #2 diesel fuel alone, for example.